Variable-speed phonograph turntable



Dec. 18, 1951 E. A. HERMSEN VARIABLE SPEED PHoNoGRAPH TURNTABLE 2 sEEE'rsF-SHEET 1 INVENTOR. EDWARD A. HER/"55N ATTORNEY 'Il llll llllllxllllll.

Filed July 2. 1949 E. A. HERMSEN VARIABLE SPEED PHONOGRAPH TURNTABLE Dec. 18, 1951 12 SHEETS-smi' 2 Filed July 2, 1949 A INVENTOR. EDWARD A. HERMSEN ATTORNEY Patented Dec. 18, 1951 VARIABLE-SPEED PHONOGRAPH A TURNTABLE Edward A. Hermsen, Honolulu,` Territory o Hawaii Y Application July 2, 1949Se1al N0. 102,860

Claims.

1 This invention relates to new and useful improvements in variable speed phonograph turntables.

Hitherto, standard phonographs have been 'equipped with turntables revolving at 78 R. P M. "Recently, manufacturers of phonograph records have offered for sale records for use in machines rotating at 45 R. P. M.' 0r 33 #/3 R. P. M. 'Such records Ywill not produce intelligible sounds if rotated at 78 R. P. M.

Accordingly, theprincipal object of the present invention is to provide a device which may be installed on conventional '78 R. P. M. lturntables and which will by suitable speed reduction-means, causev records to rotate at either 45 R. P. M. or 33.1/3 R. P. M. The invention'may also be used to rotate records at approximately R. P. M., if it should be desired to operate at that'speed. Furthermore, the invention'may easily be converted to change the speed of turntables operating at 'either 331/3 R. P. M. or l5 R. P. M. to rotate Other featuresof the present invention are the neat appearance'. and light Weight ofthe device,

i its strength and dependability.

Stillanother feature is the fact that the device is smalland occupies very vlittle space on the phonograph turntable. v

Further objects of the 'present invention .will become apparent upon reading the following specification and referring to theaccompanying drawings. in which similar .characters of reference represent corresponding parts in each-of the severalY views.

JFig.. 1 .isza vertical sectionthrough the zdevice. fFigLZ is a section :taken substantially along .the

line? 2-2 of Fig.. 1

,-Fi'g.- 3 isase'ction takensubstantiallyalong vthe Fig.V 41s" an enlarged'view -ofa-a portion .of the rim cfthefdevice. f

l Fig. 5 isfa fragmentary-section takenfsubstan tially galong' ithe, line 55;1off-Eg .-w4.

: .l Fig.fuisa?fragmentaryisectionftaken lsubstanf 2 tially along the line"6`6 of Fig. 4 with vstop arm retracted. g

Fig. 7 isa fragmentary section taken substantially along the :line 'I-l of Fig. 4.

Fig. 8 is a'fragmentarysection taken substantially along the line 8-'8 of Fig. 4.

Fig. 9 is a side elevation-drawn to reducedscale showing use of a spool ntting over the conventional spindle in order to center arecord having a large diameter center hole.

Fig. 10 is an enlarged view of a` portion of the `rim of a modification o f the invention.

InFg. lfthere is shown a conventionalrotatable phonograph turntable I5 spaced from and revolving abovea platform I6. Said turntable is rotated by amotor at a speedof '78 R. P. M. VProjecting lupwardly from r'the surface lof the turn'- table is a spindle I1- having a diameter slightly less than the 'diameter of the central hole I8 commonly formed in conventional phonograph disc record I9. The'present invention is designed to fit over the spindle I'I and'rest upon the turntable I5.

The device-is constructed about a central hub 2| having a central bore 22 flared outwardly at eitherend thereof andhaving a minimum diameterV slightly greater' thanthe diameter ofthe `spindle I1. Thus, the hub 2I is centered about the axis of the spindle I1, is easily inserted thereupon and has a minimum of frictional engagement therewith. Thek flaringf'of the central bore 22 also facilitates installation when a bent or off-set spindle'such as used in many automatic record changing machines is incorporated in the phonograph. The exterior ofhub 2 I -is threaded and at the upper end thereof is a,v projecting circumferential shoulder 23 constituting an abutment.

of...any ofthe plates with'respect v.to the others.

The upperplatezabuts shoulder 23. anda .nut

29 is .threadedupon the huhZI and bears against Vthe lowermost plate 24. A lock nut Slis-also Y.threaded .over .the hub. The.three,.plates..24, 25 and 26 arethus held centrally disposed about the axis `of. spindle I'I .but vdo not Ynecessarily rotate atfthe same speed as said spindle. The

.outery portionseof theplates are disposed substantially. parallel but .are formed so that the space-between upperplate 26 .and center :plate .25 isgreater,tha n the-distance betweenV center plate 25 and lower plate 24 so as properly to accommodate the speed reduction gears hereinafter mentioned. The lower surface of lower plate 24 is provided with a layer of felt 32 which engages turntable I5 and causes the lower plate 24 at all times to rotate with and at the same speed as the turntable. The upper surface of upper plate 26 is likewise provided with a layer of felt 33 and the disc record I9 is placed on such felt so that the record I9 at all times rotates with and at the same speed as upper plate 26.

Two annular rings 35 and 36 of substantially the same diameter are disposed between the plates. The upper ring 36 is provided with a groove 31 in its upper surface and the downwardly turned periphery 38 of upper plate 26 fits within said groove and cooperates in holding' the ring 36 centrally disposed. Similarly, the lower ring 35 is provided with a circular groove 39 in its lower face which receives the upwardly turned periphery 4I of lower plate 24. Central plate 25 fits partially between the two rings 35 and 36 and for such purpose the upper ring 36 is provided with an annular depression 42 in its lower face and the lower ring 35 is provided with a similar depression 43 in its upper face. Spaced about the rings 35 and 36 are chordal Slots 44.r Rollers 46 positioned withinthe slots 44 and screws 41 extending radially of said rings and extending through holes in the axes of said rollers provide mountings for said rollers. The rollers 46 in the upper ring 36 engage the under surface of upper plate 26 and the upper surface of central plate 25 and the rollers 46 in the lower ring 35 engage the under surface of central plate 25 and the upper surface of lower plate 24. Thus, the rollers 46 perform two functions, namely, they cooperate with the graphite washers 28 to space apart and hold in parallel alignment the plates 24, 25 and 26, and, further, they provide for free rotation of the ring 35 and 36 with respect to said plates. The inner cylindrical edges of each of rings 35 and 36 are provided with gear teeth and thus constitute circular racks 4B and 49. The rack 48 of lower ring 35 meshes with a plurality of spaced planetary gears 5| which are mounted upon central plate 25 by shafts 5Ia. Said gears 5| also mesh with ring gear 52 mounted upon lower plate 24. 'Ihere are preferably at least three such gears 5 I and hence the ring 35 is held centrally disposed by said gears and flanges 4| in grooves 39.

As will hereinabove appear, means are provided for holding the lower ring 35 stationary at the selection of the operator. Thus, rotation of the turntable I5 causes rotation of lower plate 24 and with it, ring gear 52. Since planetary gears 5| mesh both with ring gear 52 and circular rack 48, and since the circular rack 48 is held stationary this causes central plate 25 to revolve, but at a different speed than lower plate 24.

As will also further appear, means is provided for causing central plate 25 and upper plate 26 to revolve at the same speed when ring 35 is held stationary. Thus, it is possible by proper gear ratios to convert rotation of turntable |5 at 78 R. P. M. to rotation of disc record I9 at 331/3 R. P. M.

In the event that the disc record is of the type which is to be rotated at 45 R. P. M., a different gear ratio is required, and this is provided by holding upper ring 36 stationary (by means hereinafter described) and causing lower plate 24 and central plate 25 to rotate together (also by means hereinafter described) For this purpose the ring 36 is formed with a circular rack 49 On its nterior surface and a ring gear 53 is xed to central plate 25. A plurality of composite planetary gears 54 is mounted for rotation on upper plate 26 by shafts 54a. The lower part 56 of composite gear 54 meshes with ring gear 53 and the upper part 51 of composite gear 54 meshes with circular rack 49. Proper selection of gear ratios for the ring gear 53, circular rack 49, upper portion 51 and lower portion 56, cause the upper plate 26, and hence record I9 to rotate at a speed of 45 R. P. M. when the central plate 25 rotates at 7 8 R. P. M.

Each of the rings 35 and 36 is provided with means selectively operable for holding the rings stationary, as has been mentioned. Since the means foreach ring is substantially the same, only the means for upper ring 36 will be described, it being understood that ring 35 is provided with similar mechanism. A segment 6| is cut out of a portion of the upper outer edge of upper ring 36. Fitting within this cut out segment is a stop arm 62 pivotally connected adjacent one of its ends to said ring by pivot 63. Said stop arm is biased outwardly by a leaf spring 64 xed at one end to arm 62 and-bearing at its other end against ring 36. Bracket 66 holds the pivot for roller 46 where segment 6| is cut out of ring 36. Outward movement of said stop arm is adjustably limited by a block 61 adjustably positioned in an arcuate groove 68 in the surface of said ring which communicates with the cut out portion 6 I. The block 61 and inner end of stop arm 62 are arranged to abut one another and hence pivotal movement of the stoparm 62 is restrained when the surface 69 of inner end of the stop arm abuts surface 1| of block 61. Adjustment of position of block 61 thus adjusts the outward movement of stop arm about pivot point 63. Adjustability is provided by adjustment of the position of screw 12 threaded into ring 36 in arcuate slot 13 in block 61. A stationary stud 14 is xed to platform I6 and positioned outwardly from spindle I1 so that the surface 16 of the stop arm engages said stud 14 and thus rotation of ring 36 is prevented. A latch element 11 is cut into the. underside of the outer end of stop arm 62 and this latch element engages latch 18 attached to ring 36. The latch 18 is carried by one end of upwardly-biased spring 19 attached at its other end to ring 36, the spring being disposed in chordal slot 8| formed within the ring 36.

A finger catch 82 attached to the middle of spring 19 projects upwardly through a hole in ring 36 and is conveniently accessible to the operator of the machine. When the operator depresses the finger catch 82, such action forces the latch 18 downwardly anddisengages it from the cooperating latch member 11 on stop arm 62 which moves outwardly under action of spring 64. When it is desired to return the stop arm 62 to inward position, the operator moves the arm against the action of` spring 64 and the latch 18 biased upwardly by spring 19 engages the corresponding latch element11 and holds the stop arm 62 in inward position.

The stop arm 6 2 carries an inwardly projecting extension 83 which, when the stop arm is in inward position, projects into an inwardly directed groove extension 84 of the cut out portion 6I as best indicated in Fig. 6. The positioning of said extension 83 within the groove 84 forces apart a pair of horizontally extending leaf springs 86 which are normally biased to fit inside the groove extension 84. Said springs 86 are engaged by extension 63 substantially atA their midpoints. One end of eachof said springs 86 is fixed to the ring 1.3.6 pand the other fend of each spring bears aprojecting stud81 (see Fig. 8) Spaced circume ferentially about Va circle inwardly .disposed of the periphery of each vofplates 25 and 26 is a series of holes 88 slightly larger than studs 81. The studs 81 may fit within any of s aid holes when forced out of the groove extension 84 vby inward movement of extension 83 of stop varm 622 The studs 81 thus fit within the closest hole 88 and such action locks the `ring 36 which carries the studs 61 to the adjacent plates 2.5 and 26 so that the plate 2-5, ring 36 and plate 26 lall rotate together.

vWhen the stop arm 62 is projected outwardly bydepressing -catch 82 the springsv86 pull the studs 81 inwardly and thus disengage said studs from the holes 88 and permit relative movement ofthe plate 25, ring 36 and plate 26. Since outward projection of lthe stop arm 62 holds ring 36 stationary, the plate 25 and plate 26 thereuponl rotate at diierent speeds dependent upon the gear ratio of the ring gear 53, circular rack 49 and planetary gears 54'.

It will be understood that the ring 35 also bears a corresponding stop 'arm 62 and corresponding studs 81 which fitwith-in holes 88 spaced circumferentially about the plates 24 and 25 and tha-t the operator may cause the lower stop arm 62 to project outwardly by pressing lower finger catch 82 and thus hold the ring 35 stationary and permit relative rotation of the plate 24 with respect to the plate 25. When the lower stop arm 62 is positioned inwardly, the studs 81 `project into -holes 88 in plates 24 and 25 and cause the plate 24, ring 35 and plate 25r to rotate together.

Inasmuch as certain slow speed records have center holes larger than those of conventional records, a spool 9| having a hole in its axis of a diameter equal to that of spindle I1 and vhaving an outer diameter equal to that of the enlarged center holes of such records may be installedto t over the spindle I1. The spool 9I thus functions to rcenter-the large hole records and may be removed when small hole records are played. This central bore 92 of. spool. 9I is flared outwardly at each end in a manner similar to and for the same purpose asbore 22 ofY hub 2I (see Fig. 9). i

Assume that a standard 18 R; P. M. turntable I is'installed on the machine to which this device is to be attached,.andV assume further that the operator wishesto play first a 331/3 R. P. M. and thenv a 45 R. P. M. record, in order to play the 331/3 R. P. M. record the, operator first placesi thedevice on the turntable I5, the, spindle I1L of' the turntable tting into the bore 22 of hub 2:I and the felt 3.2 on the lower side .of plate 24 resting on the surface. of the. turntable .I5 andl causing the plate 24 and turntable at. all timesl to rotate at same speed. The operator thenk places the record. I9 over the spindle I1 so that it rests upon the felt 33 on the upper surface of plate 26 and hencepl'ate 26 and record I6'y at all times rotate at. the same; speed; The operator then depresses nger'catch'l 82 of lower ring- 35 which causes lower' stop arm.62v to projecttunder action of spring 64. so. that ringf 35 is. he'ldstationary'by permanent projection I4 attached to the platform I6 ofthe machine. When the stop arm 62 'projectsvandf' hence extension 83 moves out of the groove: extension 84.'` in ring 35, -thel studs. 61vr move inwardly and are disengaged from. theholes 88. in plates 24; and 2.5 thus. permitting relativeerotation of. platef24 andzplateq2-5x. The machinev is then. started..v lRotation of f thefturnf.

table :I5 at '18 vR.P. M. causes the ring gear 52 which is xed to plate 24 to rotate at the -same speed. Because of the gear ratio between ring gear '52, circular rack 48 and planetary gear 5I., the center of said planetary gear 5l and hence plate 25 to which it is mounted rotate at a speed of` 331/3 R. P. M. `Since the stop arm 62 of upper ring 3'6 is retracted and hence studs 61 azlxed to said ring 36 are projected into holes 88 in plates 25 and '26, plate 26 rotates at 331/3 R. P. M. Hence, record I9 rotates at such speed.

' When it is desired to use a record having a 45 R. P. M. speed, the stop arm 62 of lower'ring 35 Vis retracted by the operator, thus causing the studs 81 aiixed to ring 35 to engage within holes '68 in plates 24 and 25, and thus causing the center plate 25 to rotate at the same speed as turntable I5. The operator depresses the linger catch 82 of upper ring 36 which allows the stop arm 62 to project under action of its spring 64 and engage the stationary projection 14 on platform I6. Thereupon, ring 36 is held stationary. The same action of projecting the stop arm 62 likewise permits the studs 81 of upper ring to disengage from holes 3B in plates 2,5 and 26 hence permit relative rotation of plates 2 5 and'26.

The operator then starts the machine which causes ring gear 53 to rotate at '18 R. P. M. Planetary gear portion 56 meshing with said ring gear 53V and iixed to planetary gear portion 51, which meshes with circular rack'49 of .ring 36 causes the 'axis of planetary gear 54 and upper plate 26 to which it is pivotally connected to rotate at a speed'l of 45 R. P. M. which, therefore, causes the record I6 to rotate at such speed.

It will be understood that if a '18 R. P.'M. rec:- ord is to be played the operator may either remove the device from the turntable or leave the device on the turntable and retract both stop arms 62 in lower ring 35 and in upper ring 36. When both stop arms 62 are retracted studs 81 in lower ring 35 lock lower plate 24 and center plate. 25 together, and studs 81 in upper ring 36 lockv center plate 25 and upper plate 26 together.

" Thus, the record I9. rotates at the same speed.` as

turntable I5'-i. e., 78 R. P. M.

If it is desired to rotate the record at some other speed, such as approximately 25 R. P. M., both. stop arms 62 are projected which causes bothlower ring 35 and upper ring 36 4to be held.

stationary and all of thestuds 81 to be retracted so astoA permit all three plates 24," 25 and 26 to revolveat different speeds. Ring gear 52 revolves at 78 R. P. M. and the axis lor planetary gear 5I which meshes with both said ring gear 52 and stationary'circular rack 48 rotates at 331/3 R. P. M. whichcauses center plate 25 and ring gear 53 to rotate at 331/3 R. P. lVI. Such speed of rotation of ring gear 53 results in av speed of rotation of upper plate 26 of approximately `25 R. P.' M.

If through accident the operator installs the device upside down, no harm results. because projection of the stop` arms 62 does not result in the rings 35V and 36 being held stationary, for the' momentarily retracting againsty the pressure ofi springs 66. Of course, projection of the stop arms 62 permits. relative movement of theA adjacent plates; 24,. 25: and 2.6 and hence the actualspeed of the. record Ifis indeterminant, beingdepend'-v entuponthe. frictional resistance of the various rela-tively.v moving; parts.` The operatorfthussoon.`

7. becomes aware that the device has been installed upside down and rectifies the situation.

Thefdevice may be modied so as to convert turntables rotating at 331/3 R. P. M. or 45 R. P. M. to 78 R. P. M. This modication entails the installation of additional stop arms 94 which project in a direction opposite from arms 62 as shown in Fig. 10. It will be understood that in this modication the entire device is turned upside down so that the plate 26 engages the turntable l5 and the record I9 rests upon the plate 24 (i. e., opposite from normal use). Stop arms 93 are pivotally attached by pivots 94 to arms 82 and have curved surfaces 95 projecting in a direction opposite from surfaces 16. Said arms are biased outwardly by springs 96 which encompass pivots 94 and opposite ends of which bear against arms 62 and 93 respectively. The inner ends of arms 93 carry rollers 91 which travel within a recess 98 in out out segment 6l. Said rollers 91 nest in curved abutments 99 which limit movement of the rollers longitudinally of recess 98. Stop arms 93 on the rings 35 and 36 engage projection 14 on platform I 6 and selectively either hold ring 35 or ring 36 stationary or lock or unlock the plates 24, 25 and 26 from rotation with each other. The gear ratio between the various intermeshing members thus results in arecord speed of 78 R. P. M. for a turntable speed of either 331/3 R. P. M. or 45 R, P. M., the operator selecting the proper stop arm 92 for projection dependent upon the speed of the machine to which the device is attached.

It will also be seen that by proper use of this device a turntable speed of 45 R. P. M. may be converted to 331/3 R. P. M. or vice versa.

It will be apparent that this device may be used on phonographs having automatic record changing attachments as well as those playing records singly.

The invention has been described in rather complete detail by way of reference to example and illustration for purposes of clarity of understanding, but various changes and modifications in use, design and assembly may be practiced Within the spirit of the invention and scope of the appended claims.

I claim:

1. A variable speed turntable comprising; a iirts apertured rotatable plate, a second apertured rotatable plate, a rst ring gear xedly mounted on said rst rotatable plate, a second ring gear partially interposed between said plates and rotatable with respect to each said plate and arranged for rotation coaxially with respect to said plates, a planetary gear rotatably mounted on said second plate, said planetary gear meshing with both said ring gears, and means selectively operable by the operator for locking said lirst and second plates for rotation together, including an extensible arm carried by said second ring gear, and a pair of studs carried by said second ring gear, each of said studs being biased away from one of said plates, said arm being arranged when retracted to urge each said stud into an aperture in the respective plate toward which said stud is biased.

2. A variable speed turntable Vfor use adjacent a stationary projection comprising; a rst apertured, rotatable plate, a second apertured, rotatable plate, a iirst ring gear iixedly mounted on said first rotatable plate, a planetary gear rotatably mounted on said second rotatable plate, a second ring gear independent of said plates and partially interposed therebetween and arranged s] for rotation coaxially with respect to said plates, said planetary gear meshing with both said ring gears, and means selectively operable by the operator for movement to two positions, one position holding said second ring gear stationary and the other position locking said rst and second plates for rotation together, said means comprising an extensible arm carried by said second ring gear, movable to outward and inward positions and engageable when in outward position with said stationary projection, a pair of studs carried bysaid second ring gear, each of which is spring biased away from the respective plates which they face, and means on said arm arranged when said arm is in inward position to urge said studs toward and into engagement with apertures in the respective plates which they face.

3. A turntable as claimed in claim 2 which also includes latch means carried by said arm, cooperating latch means carried by said second ring gear, and means manually operable for disengaging said latch means from each other.

4. A variable speed turntable comprising, a rst rotatable plate, a second rotatable plate, a third rotatable plate, a rst ring gear independent of said plates and partially interposed between said rst plate and said second plate, a second ring gear independent of said plates and partially interposed between said second plate and said third plate, a first sun gear xedly mounted on said rst rotatable plate, a rst planetary gear rotatably mounted on said second rotatable plate and meshing with both said rst sun gear and said rst ring gear, a second sun gear mounted on said second rotatable plate, a second planetary gear meshing with both said second sun gear and said second ring gear and rotatably mounted on said third plate, and means selectively manually operable by the operator for holding said rst ring gear and said second ring gear stationary.

5. A turntable as claimed in claim 4 for use adjacent a stationary abutment in which said means comprises extensible stop arms carried by eachof said second ring gear and said first ring gear and selectively engageable with said stationary abutment.

6. A variable speed turntable comprising, a rst rotatable plate, a second rotatable plate, a third rotatable plate, a first ring gear independent of said plates and partially interposed betweenr said rst plate and said second plate, a second ring -gear independent of said plates and partially interposed between said second plate and said third plate, a iirst sun gear xedly mounted on said first rotatable plate, a rst planetary gear rotatably mounted on said second rotatable plate and meshing with both said iirst sun gear and said rst ring gear, a second sun gear mounted on said second rotatable plate, a second planetary gear meshing with both said second sun gear and said second ring gear and rotatably mounted on said third plate, means selectively operable by the operator for locking said rst plate and said second plate for rotation together, and means selectively operable for locking said second plate and said third plate for rotation together.

7. A turntable as claimed in claim 6 in Which said plates are apertured and in which said means comprises extensible arms carried by each of said ring gears, and studs carried by each of said ring gears biased away from the plates which they face, said arms being arranged when retracted to urge said studs into apertures in adjacent plates.

8. A Variable speed turntable comprising, a nrst rotatable' plate, afsecond rotatable plate, a third 9 rotatable plate, a first ring gear independent of said plates and partially interposed between said rst plate and said second plate, a second ring gear independent of said plates and partially interposed between said second plate and said third plate, a first sun gear xedly mounted on said rst rotatable plate, a first planetary gear rotatably mounted on said second rotatable plate and meshing with both said rst sun gear and said first ring gear, a second sun gear mounted on said second rotatable plate, a second planetary gear meshing with both said second sun gear and said second ring gear and rotatably mounted on said third plate, rst means selectively manually operable for movement to two positions, one position holding said rst ring gear stationary and the other position locking said first and second plates for rotation together, and second means selectively manually operable for movement to two positions, one position holding said second ring gear stationary and the other position locking said second and third plates for rotation together.

9. A turntable as claimed in claim 8 and wherein is provided a stationary projection, in which said plates are apertured and in Whicheach of said means comprises an extensible arm carried by its respective ring gear, movable to outward vand inward positions and engageable when in outward position with said stationary projection,

a pair of studs carried by said ring gears, each of which is spring biased away from theplates which they face, and means on each of said arms arranged when said arms are in inward position to urge said studs toward the plates which they face and into engagement with apertures in adjacent plates.

10. A variable speed turntable for use adjacent a stationary stud, said turntable comprising, a central interiorly bored hub, said hub being exteriorly threaded, a first plate, a second plate, a

third plate, each of said plates fitting about and being held concentric with respect to said hub, washers interposed between said plates adjacent said hub, means for securing said plates centrally disposed with respect to said hub and freely rotatable with respect to said hub and with respect to each other, a rst ring gear surrounding and partially interposed between said first plate and said second plate, a second ring gear surrounding and partially interposed between said second plate and said third plate, rollers carried by each of said ring gears engaging adjacent plates and holding said plates parallelly disposed, a first sun gear fixed to said first plate, a rst planetary gear rotatably mounted on said second plate and meshing with said iirst sun gear and said rst ring gear, va second sun gear iixed to said second plate, a second planetary gear rotatably fixed to said third plate and meshing with said second sun and with said second ring gear, a rst stop arm attached to and extensible from said rst ring gear and'engageable with said stationary stud to hold said first ring gear stationary and cause relative movement of said first plate with respect to said second plate, and means carried by said rst ring gear and actuated upon retraction of said stop arm to lock said rst plate and second plate for rotation together.

EDWARD A. HERMSEN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,353,370 Sears July 11, 1944 FOREIGN PATENTS Number Country Date 340,905 Great Britain Jan. 8, 1931 422,473 Great Britain Jan. 10, 1935 

